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Bioengineering Aids to Reproductive Medicine
Published in Sujoy K. Guba, Bioengineering in Reproductive Medicine, 2020
In order to maintain simplicity in the design and construction most rigid endoscopes have a fixed focus. Even so the design is such that objects within a certain range of distance from the objective are fairly well focused and this range is the depth of focus. Power of accommodation of the eye also helps in viewing objects at varying distances and the accommodation increases the range beyond the intrinsic depth of focus of the instrument. An older observer with reduced power of accommodation will obviously be able to clearly see objects over a smaller range of distance than a younger endoscopist with normal amplitude of accommodation which usually ranges from infinity to 25 cm in front of the eye. The difference between the intrinsic depth of focus of an endoscope and the effective range of focus as viewed by an observer has important bearing in photography through an endoscope. An observer may see an object clearly through an endoscope but the picture taken may come out as blurred. This may be because the observer has exerted his power of accommodation to bring the object into focus whereas the camera obviously does not have this provision. Modern endoscopic cameras are provided with focusing arrangement which is independent of the power of accommodation of the photographer’s eye.
Rehabilitation and management of visual dysfunction following traumatic brain injury
Published in Mark J. Ashley, David A. Hovda, Traumatic Brain Injury, 2017
Patient B.B. was seen for examination 4 months postinjury. He had no light perception from his right eye due to optic nerve atrophy following his injury. His left eye was healthy and intact. He presented with decreased acuity (20/80 when reading a vertical column and 20/30 when reading horizontally). He had reduced contrast sensitivity for medium spatial frequencies. He also had a left hemianopia with macular sparing. He had difficulty reading. He watched his feet when walking and tended to veer leftward. Saccades were slow and pursuits were jerky. He had a reduced amplitude of accommodation and was already wearing a bifocal correction, which he found useful. He read at approximately 8 inches from his eyes for the additional magnification.
Near work symptoms and measures of accommodation in children
Published in Clinical and Experimental Optometry, 2023
Angela M Chen, Eric J Borsting
Direct comparison of the present study to previous studies investigating associations between the amplitude of accommodation and CISS scores is difficult due to methodological differences.1–3 These studies found that children with reduced amplitude of accommodation had higher CISS scores when compared to children with normal binocular vision. The results of the present study are consistent with these studies as the symptomatic children in the present study exhibited a lower amplitude of accommodation. However, a recent study by Pang et al.18 did not find an increase in symptoms as measured by the CISS in children with reduced amplitude as measured by the minus lens method and no vergence disorders. In contrast to Pang et al.,18 participants in the present study were selected based on symptoms, not the presence or absence of accommodative insufficiency or oculomotor dysfunction, and this makes comparisons of the present study results to those of Pang et al.18 difficult. In addition, Pang et al.18 did not measure accommodative facility in their population, and this clinical measure showed the largest difference between the symptomatic and asymptomatic groups in the present study and was most associated with symptoms.
Impact of dual-focus soft contact lens wear on near work-induced transient myopia
Published in Clinical and Experimental Optometry, 2023
Raimundo Jiménez, Beatriz Redondo, Tomás Galán, Pedro Machado, Rubén Molina, Jesús Vera
All participants were examined at a baseline visit to determine the fulfilment of the following inclusion criteria: (i) between −0.50 D and −6.00D of spherical error and less than 1.00D of astigmatism, (ii) best-corrected distance visual acuity of at least 0.0 logMAR in each eye, (iii) a myopic anisometropia lower than 2.00D, (iv) free of any systemic/ocular disease or current use of systemic medication, (v) no history of strabismus or amblyopia, (vi) a normal range of amplitude of accommodation, as calculated by the Hofstetter’s formula,36 (vii) fusion in near and far vision, as assessed by the standard Worth-4-dot test (viii) 50 sec of arc of near stereoacuity, and (ix) belong to the asymptomatic group (score< 24) using the Conlon survey.37 The protocol was approved by the University of Granada Institutional Review Board (IRB approval: 1786/CEIH/2020) and adhered to the tenets of the Declaration of Helsinki. An individual informed consent was obtained from all participants.
Screening for convergence insufficiency in school‐age children
Published in Clinical and Experimental Optometry, 2018
Anne M Menjivar, Marjean T Kulp, G Lynn Mitchell, Andrew J Toole, Kathleen Reuter
Monocular amplitude of accommodation was assessed using a single column of letters of 6/9 equivalent at 40-cm and a near point rule. The first sustained blur was considered the endpoint. Accommodative amplitude was measured three times (right eye only, recorded to the nearest half‐centimetre) and the mean was used for analysis. Monocular accommodative facility was measured using ± 2.00-D lens flippers and a single column of letters of 6/9 equivalent on a hand‐held fixation target held at 40-cm. The subject was instructed to try to get the letters clear as quickly as possible, and to report (by saying ‘clear’) as soon as the letters were clear. Monocular accommodative facility (cycles/minute) was assessed only on the right eye. Binocular accommodative facility was also assessed using a Suppression Vectogram number 9 and Polaroid filter glasses (Stereo Optical, Chicago, Illinois, USA).